1. The Field of the Invention
The present invention relates to reduction jacks used for reducing spinal rods into rod channels of bone fixation screw.
2. The Relevant Technology
There are a number of surgical procedures and treatments that require the immobilization of a portion of the spine. For example, vertebral fusion is a medical procedure where adjacent vertebrae of the spine are fused together. As part of this procedure, a mechanical stabilizing system is implanted in the patient which immobilizes the adjacent vertebrae. Such stabilizing systems can also be used in the treatment of spinal trauma and spinal curvature such as scoliosis.
A typical spinal stabilizing system includes, in part, a plurality of bone fixation screws that are mounted on each side of each consecutive vertebra that is being fused together. Each bone fixation screw has a collar with a U-shaped rod channel formed thereon. An elongated, metal, spinal rod is received within the rod channels of the aligned bone fixation screws on each side of the spine. Once the spinal rods are positioned, fasteners are threaded onto the collars so as to rigidly lock the spinal rods to the bone fixation screws, thereby securing each vertebra in a fixed relative location.
Because the vertebrae are often out of alignment at the start of the procedure, the spinal rods may freely be received within some of the rod channels of the bone fixation screws but may be misaligned with others. To that end, reduction jacks are used to reduce or move the spinal rods into the rod channels from which the spinal rods are misaligned.
A reduction jack typically includes a base that removably mounts to the bone fixation screw and captures the spinal rod, a reducer that engages the base, and a mechanical drive assembly. The drive assembly is manually operated and is used to move the reducer relative to the base so that the reducer pushes against the spinal rod and forces the spinal rod into the rod channel of the bone fixation screw. Moving the spinal rod into the rod channel can occur as a result of moving the spinal rod and/or the corresponding vertebrae.
Although reduction jacks are useful for their intended purpose, they typically have a number of shortcomings. For example, the drive assembly typically moves the reducer at a very slow rate. As such, it can take an extended period of time to even move the reducer to the point where it initially engages the spinal rod. It can also take an extended time period to move the reducer back to its original position so that the reduction jack can be removed from the bone fixation screw. In addition to being time consuming to use, conventional reduction jacks can be difficult to attach to the bone fixation screws. Likewise, in conventional reduction jacks it can often be difficult to access and/or manipulate the drive assembly that moves the reducer relative to the base. Furthermore, some conventional reduction jacks can obstruct the bone fixation screw making it difficult to align and attach the fastener to the bone fixation screw.
Finally, the reduction jacks can also be used as a lever, when attached to a bone fixation screw, to move the vertebrae to a desired position or orientation. Conventional reduction jacks can often be too long or too short for their desired placement and use.
Accordingly, what is needed in the art are reduction jacks that overcome one or more of the above shortcomings.